Migrate guide to `pyos-sphinx-theme` and clean up static files

[Revathyvenugopal162]

Description:

Since the pyos-sphinx-theme is now available on PyPI, we can proceed with migrating the guide to use this package.

Tasks:

1. Migration:

   • Migrate the guide to use the pyos-sphinx-theme package.

2. Clean-Up:

   • Remove all static files associated with the current pydata-sphinx-theme.

3. Testing:

   • Thoroughly test the pyos-sphinx-theme to ensure compatibility and functionality across the documentation.

4. Adjustments:

   • Make any necessary adjustments to the configuration and layout after migration